Her bridal processional music will be the soaring choral masterpiece "I was glad" by Sir Charles Hubert Hastings Parry from Psalm 122.

It was composed for the crowning of Prince William's great-great-great grandfather Edward VII at Westminster Abbey in 1902, but is also popular at weddings.

Its instrumental introduction will allow the bride to take her place at the Great West Door on the green marble memorial stone to Sir Winston Churchill.

As the choir begins to sing, she will begin her three and a half minute procession through the Nave and Quire to meet her Prince on her father's arm.

Before Miss Middleton will be an "avenue of trees" made up of six English Field Maples and two Hornbeams - some 20ft tall - with the abbey decorated in white, green and cream foliage.

A St James's Palace spokesman said: "The music will build up before the words begin. It will be quite dramatic. A lot of these pieces have been chosen for their theatre.

"They are stunning pieces of music that fill the Abbey and give a sense of grandeur to the occasion."

The spokesman said The Introit will not be the version used at Coronations, where it is sung as an entrance anthem with additional "Vivat" proclamations.

It was used as The Anthem for the 1981 wedding of Prince William's parents the Prince of Wales and Lady Diana Spencer, but Diana walked up the aisle to The Trumpet Voluntary by Jeremiah Clarke.

Parry's version was revised in 1911 for the coronation of King George V, when the introduction was added.

It also featured in the Queen's coronation in 1953 as she processed through the Nave and Quire to her Chair of Estate.

Parry, said to have composed some of the most moving choral pieces of the Victorian and Edwardian eras, also wrote the music for William Blake's popular hymn Jerusalem and John Milton's Blest Pair of Sirens - both of which feature in William and Kate's ceremony.

The words of "I Was Glad" from Psalm 122: 1-3, 6-7 read: "I was glad when they said unto me: We will go into the house of the Lord.

"Our feet shall stand in thy gates: O Jerusalem.

"Jerusalem is builded as a city: that is at unity in itself.

"O pray for the peace of Jerusalem: they shall prosper that love thee.